<!DOCTYPE HTML>
<html>
<head>
  <title>Test that we don't get unnecessary repaints due to subpixel shifts</title>
  <script type="application/javascript" src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"></script>
  <script type="text/javascript" src="chrome://mochikit/content/tests/SimpleTest/paint_listener.js"></script>
  <link rel="stylesheet" type="text/css" href="chrome://mochikit/content/tests/SimpleTest/test.css"/>
</head>
<!-- Need a timeout here to allow paint unsuppression before we start the test -->
<body onload="setTimeout(startTest,0)">
<div id="t" style="width:400px; height:100px; background:yellow; overflow:hidden">
  <div style="height:40px;"></div>
  <div id="e" style="height:30px; background:lime"></div>
  <div style="height:60.4px; background:pink"></div>
</div>
<pre id="test">
<script type="application/javascript">
SimpleTest.waitForExplicitFinish();

var t = document.getElementById("t");
var e = document.getElementById("e");
var utils = window.QueryInterface(Components.interfaces.nsIInterfaceRequestor).
               getInterface(Components.interfaces.nsIDOMWindowUtils);

function startTest() {
  // Do a scroll to ensure we trigger activity heuristics.
  waitForAllPaintsFlushed(function () {
    t.scrollTop = 5;
	// Scroll down as far as we can, to put our rendering layer at a subpixel offset within the layer
    waitForAllPaintsFlushed(function () {
      t.scrollTop = 1000;
      waitForAllPaintsFlushed(function () {
        // Clear paint state now and scroll again.
        utils.checkAndClearPaintedState(e);
		// scroll up a little bit. This should not cause anything to be repainted.
        t.scrollTop = t.scrollTop - 10;
        waitForAllPaintsFlushed(function () {
          var painted = utils.checkAndClearPaintedState(e);
          is(painted, false, "Fully-visible scrolled element should not have been painted");
          SimpleTest.finish();
        });
      });
    });
  });
}
</script>
</pre>
</body>
</html>
